Claim outstanding - no response from GEMS

Claim still outstanding: 09-10-2017 Member nr ********** 89. I phoned on 01-12-2017. MH ********** 2. On 06-12-2017 I tried to reprocess claim. On 15-02-2018 I sent a query to ********** and on 06-03-2018 I sent a query to ********** On GEMS's newest remittance I receive a message: claim stale. What can I do? Christa from practice nr ********** .